In a prior art, there has been used a screen printing method to form an electrically conductive paste film corresponding to the electrical conductor pattern for the electronic component on the ceramic green sheet by the thick film processing (see the patent document 1).
FIG. 4 shows the method for forming the electrically conductive paste film corresponding to the electrical conductor pattern for the electronic components on the ceramic green sheet by the thick film processing according to the prior art. This method will be described in details with reference to FIG. 4 hereinafter.
In this prior art, a mesh-like screen 62 patterned corresponding to an electrical conductor pattern is superposed on a ceramic green sheet 61 as shown in FIG. 4(a) and thereafter an electrically conductive paste 63 is coated on the screen 62 by a squeegee 64 as shown in FIG. 4(b). In FIG. 4(a), a reference numeral 621 designates a non-opening portion of the screen 62 and a reference numeral 622 designates an opening portion of the screen 62. In FIG. 4(b), a reference numeral 631 designates an electrically conductive paste film formed by being filled in the opening portion 622 of the screen 62.
After the electrically conductive paste 63 is coated, the screen 62 is removed out of the ceramic green sheet 61 as shown in FIG. 4(c), so that the electrically conductive paste film 631 is left on the ceramic green sheet 61. The ceramic green sheet 61 and the electrically conductive paste film 631 are sintered after dried to form a ceramic electronic component.
Since the method for manufacturing the electronic component according to the prior art uses the mesh for the screen 62, it is difficult to reduce the width of the electrically conductive film due to the relation of the wire diameter of the mesh. As noted from FIG. 4(d), the electrically conductive paste film 631 of non-dried layer not solidified flows so that its skirt is expanded when the screen 62 is removed out of the ceramic green sheet 61. Thus, the electrically conductive paste film 631 has the width widened and in addition thereto, the cross section thereof gets roundish so that its rectangular shape collapses as shown in FIG. 4(d).
Of late, there has been a large demand of an electrical conductor pattern of high fineness and high density for a ceramic electronic component and a multi-layering of the component has been progressing. The conventional method for manufacturing the ceramic electronic component according to the prior thick film processing cannot disadvantageously meet these demands.
Meantime, an electrically conductive film for a semiconductor IC or the like has been formed by a lift-off method, which is one of thin film processing such as vapor deposition, sputtering and so on (see Patent Document No. 2).
A method of forming the electrically conductive thin film by the lift-off method of the prior art is shown in FIG. 5 and will be explained with reference to FIG. 5. After a photo-resist 72 is coated on a substrate 71 as shown in FIG. 5(a), the photo-resist 72 is patterned corresponding to an electrically conductive pattern by a photolithography method to form opening portions 721 and non-opening portions 722.
Thereafter, vapor particles or ion particles of electrically conductive materials are radiated onto the substrate 71 in the direction indicated by arrows by means of vapor deposition, sputtering, CVD (chemical vapor deposition) and so on. The particles of the electrically conductive materials are stuck and deposited onto the substrate 71 by the radiation energy to form the electrically conductive film 73 as shown in FIG. 5(b). The electrically conductive film portions deposited on the opening portions 721 are designated by a reference numeral 731, those deposited on the non-opening portions 722. are designated by a reference number 732 and those deposited on the side face of the non-opening portions 722. are designated by a reference number 733.
Then, the electrically conductive layer 73 is lightly etched to remove the electrically conductive film 733 deposited on the side face of the non-opening portions 722 as shown in FIG. 5(c) whereby the electrically conductive films 731 and 732 are separated from each other. Finally, the photo-resist 72 and the electrically conductive film 732 on the photo-resist 72 are removed whereby just the electrically conductive film 731 is left on the substrate 71 as shown in FIG. 5(d).
The method of forming the electrically conductive film by this lift-off method can obtain the highly fine and dense electrically conductor patterns because the electrically conductive thin film can be formed. However, since the electrically conductive film is formed by sticking and depositing the vapor particles or the ionic particles of electrically conductive materials onto the substrate, the electrically conductive thick films cannot be formed and the lift-off method cannot disadvantageously form the electronic component of multi-layer construction by laminating a number of substrates having the electrically conductive films provided thereon. Furthermore, since the lift-off method forms the electrically conductive films by the vapor deposition and so on, the steps and the apparatus for forming the electrically conductive films are disadvantageously complicated.
Patent Document 1: JP08-118467 A1
Patent Document 2: JP05-62948 A1